Fracturing of wells



R. H. ALLEN FRAGTURING OF WELLS Aug. 17, 1965 Filed Nov. 2v, 1961 k 4 i I i l l l l l l l v W, l l I i INVENTOR RICHARD H. ALLEN @uw EN@ 551% s Aug. 17, 1965 R. H, ALLEN 3,200,882

` FRACTURING OF WELLS Filed Nov. 27, 1961 2 sheets-sheet 2 INVENTOR RICHARD H. ALLEN 73H5 Dim?" Swm United States Patent O 3,200,882 FRACTURIN G OF WELLS Richard H. Allen, Charleston, W. Va., assignor to Well Service Incorporated, Charleston, W. Va., a corporation of West Virginia Filed Nov. 27, 1961, Ser. No. 155,003 6 Claims. (Cl. 166-42) This invention relates to new and useful improvements in the fracturing of Wells such as water, oil, and gas wells.

The process of fracturing wells is generally practiced in order to initiate and/ or increase the output of the well. Fracturing involves the opening, the widening, and/ or removing of the deposits and obstructions from the producing strata in the well bore. The fracturing may be effected chemically by dissolving the deposits or obstructions in the producing strata as for example in acid fracturing or may be effected mechanically by physically forcing the strata open as in hydraulic fracturing in which liquid under pressure is forced into the producing strata in order to open the same up and increase the production.

The invention relates to a mechanical fracturing process and the objects thereof will become apparent from the following description read in conjunction with the drawings in which;

FIG. l diagrammatically shows a water well and an embodiment of a fracturing apparatus in accordance with the invention in an initial stage of operation;

FIG. 2 diagrammatically shows the apparatus of FIG. 1 in an intermediate stage of operation;

FIG. 3 shows the apparatus of FIG. 1 in a final stage of operation; and

FIG. 4 is a side elevation partially in section of a portion of a further embodiment of an apparatus in accordance with the invention.

The fracturing in accordance with the invention is eifected by maintaining a body of liquid in the well to be treated above the level of the strata to be fractured and suddenly releasing a high pressure gas in the well from a point spaced above said body of liquid to expand at high velocity against said body delivering a sudden shock-like blow to the liquid, forcing the liquid into the strata and fracturing the same.

Preferably, a high pressure pipe is run into the well and sealed to the well bore by a conventional packer. The bore of the high pressure pipe is sealed at a point within the well while a gas cap is maintained below the seal between it and the body of liquid in the well. Compressed gas is then forced into the pipe above the seal to build up a pressure of at least 1,000 lbs. per sq. inch and preferably between 2,000 and 3,000 lbs. per square inch while the pressure of the gas cap below the seal is maintained at not more than about 1A@ of the pressure built up above the seal. The seal is then suddenly released. as for example by causing the same to rupture so that the gas expands through the air cap striking the body of liquid and forcing the same into the producing strata in order to fracture the well.

Referring to the embodiment as shown in FIGS. 1 3 of the drawing, 1 represents a conventional water well with, for example a 6" bore drilled through bed rock. Water is supplied to the well from the strata 2. The well bore is lled with water 3 to above the level of the strata 2 either by allowing the water level in the well to build up per se or by pumping in additional water from an external source. Conventional additives used in hydraulic fracturing, as for example, propping agents such as Ottawa silicas and -10|20 mesh to -204-40 mesh or plastic beads or aluminum pellets in amounts of one-half pound to three pounds per gal. of liquid may be used.

A conventional high-pressure pipe 4 is run into the CFI lCe

well preferably terminating in the area of the producing strata to be fractured. The pipe may, for example, be in a 6" well a 3 diameter pipe of steel or the like. The pipe may be run in sections, screwed together in the conventional manner with pressure-tight joints. The lower portion of the pipe 4 is then sealed to the well bore by means of the conventional packer 5, the packer may, for example, be in the form of a rubber sleeve sealed between two telescopic sections of pipe which are collapsed together forcing the rubber sleeve to expand in pressure-tight sealing contact with the bore of the well. It is, of course, possible, however, to use any known conventional or commercially available packer. The bore of the pipe 4 is provided with the seat 6 as for example of metal welded or press-tted to the bore of the pipe. A mobile sealing device is then inserted into the top of the pipe. This mobile sealing device may consist of the rubber sleeve 7 which engages with a sliding it within the interior of the pipe and which has the metal pipe section 8 bonded thereto. The pipe section S is sealed with the rupturable disc 9. This rupturable disc is of the conventional and well-known construction and merely consists of a dise of metal, plastic or the like which will rupture at a predetermined pressure. The dise may, for example, be constructed to rupture at a pressure between about 2,000 and 3,000 lbs. per square inch pressure.

The top of the pipe 4 is then sealed and a source of high pressure gas is connected thereto. This may conveniently consist of a conventional high-pressure air compressor diagrammatically shown at 10 -or high-pressure gas tanks, as for example air tanks, pressure nitrogen tanks, CO2 etc. The high-pressure gas is then forced into the pipe above the mobile sealing device 789 and forces the same down through the bore of the pipe 4 until the rubber sleeve 7 seats against the seat 6 as shown in FIG. 2. As the mobile sealing device is forced down through the bore of the pipe 4, air will be trapped therebelow forming the air cap 11 between the bottom of the rupturable disc 9 and the body of the water 3. The distance between the disc and the water, i.e. the height of the air cap above the water should be at least 10 feet and preferably between about l0 and 20 feet and the pressure `of the air cap must not exceed more than 1/10th of the pressure which is ultimately built up above the disc prior to rupture. The gas pressure is then continuously built in the pipe 4 until the disc 9 ruptures. The high pressure gas, such as the air then expands at high velocity through the ruptured disc and air cap striking the body of water 3 with a hammer-like blow. The water acting under the dynamic kinetic impact of the air or other gas and under the influence of the pressure is forced into the strata 2 `opening the same to increase the production of the well.

If it is desired to repeat the operation, a further mobile sealing device may be forced through the pipe to seat on top of the first run mobile sealing device whose disc had initially been ruptured, and the operation may be repeated.

Generally, a pressure of at least 1,000 lbs. per square inch, and preferably between about 2,000 and 3,000 lbs. per square inch should be built up in the pipe 4 before being released through the sealing device to expand through the air cap and strike the water body.

In place of the rupturable disc, any other known or conventional sealing device may be used to provide the same allows a sudden opening and release of the pressure from above therethrough. Thus, conventional quick-acting valve means may be used. As shown in FIG. 4, an embodiment of the sealing device consists of a flange 12 provided with a central bore opening in the form of a seat for a ball valve. The flange 12 is sealed to the inner wall of the pipe 4 by means of welding or in any other known or conventional manner. A deformable ball 13, as for example a rubber ball is allowed to seat on the opening of the ange 12 and is dimensioned with respect to the size of the opening of the flange 12 so that the ball will be forced through the opening in the flange 12 after a predetermined gas pressure is built up thereabove.

With a sealing device of this type, repeated operations may be achieved by simply dropping further balls 13 into the pipe. As a practical example for fracturing a water well, 250 feet deep, with a 6" diameter bore, drilled in bed rock, and having the producing strata at about 175 feet a steel high-pressure pipe 3 in diameter may be run to a depth of about 160 feet and sealed olf with a conventional rubber seal-olf packer to the wall of the well. Water may then be pumped into the well to a height of 50 feet above the packer setting position. A mobile sealing device as shown in FIGS. 1-3, is then placed in the pipe and provided with a rupture disc set to rupture at a pressure between about 2,000 and 3,000 lbs. per square inch. Compressed air from a high-pressure air cornpressor is then forced into the pipe above the mobile sealing unit forcing the mobile sealing unit to the bottom of the pipe seating the same against a seat corresponding to the seat 6 in FIGS. 1, 2, and 3. This causes an air cap to be built up above the water level to a designed height of 10 to 20 feet and with a pressure between about 200- 300 lbs. per square inch. Pressure is then built up within the high-pressure pipe to between about 2,000 and 3,000 lbs. per square inch at which point the disc ruptures forcing the high-pressure air to expand at high velocity striking the body of water and forcing the same to fracture the producing strata.

In the same manner, producing gas and/or oil wells may be fractured. In connection with fracturing gas and oil wells, it is preferable to us water, oil, or acid as the liquid and N2 and CO2 as the compressed gas.

It must be noted with emphasis that in accordance `with the invention the water is not merely forced into the strata in order to fracture the same by means of the high-pressure gas but due to the sudden release of the highapresure gas, through the air cap, not only the effective pressure of the gas acts on the water for the fracturing, but the kinetic energy of the gas, as the same expands at high velocity through the air cap, acts in a shock-like and explosive manner on the water producing an explosive-like fracturing while avoiding the danger and contamination which would be involved in the use of explosives.

While the invention has been described in detail with reference to certain specific embodiments, various changes and modifications which fall within the spirit of the invention and scope of the appended claims will become apparent.

The invention, therefore, is only intended to be limited by the appended claims or their equivalents wherein I have endeavored to claim all inherent novelty.

I claim:

1. A process for fracturing wells which comprises running a high-pressure pipe into the well and providing a seal between the high pressure pipe and the well wall above the strata to be fractured, maintaining body of liquid in the well at the level of the strata to be fractured, sealing the bore of said pipe at a point within the well and maintaining a gas cap below said seal between it and said body of liquid, compressing gas in said pipe above said seal to a pressure of at least 1,000 lbs. per sq. inch while maintaining the pressure of said gas cap at not more than about 1A() of said pressure above said seal and suddenly releasing said pressure through said seal.

2. A process according to claim 1 in which said pressure is released through said seal by rupturing said seal.

3. Process according to claim 1 in which said gas is compressed in said pipe above said seal to a pressure of at least 2,000 lbs per sq. inch.

4. Process according to claim 3 in which said gas is compressed in said pipe above said seal to a pressure between about 2,000-3,000 lbs. per sq. inch.

5. A process for fracturing water wells which comprises running a high-pressure pipe in the well and providing a seal between the high pressure pipe and the well wall above the strata to be fractured, maintaining a body of water in the well adjacent to and extending to above the strata to be fractured, sealing the bore of said pipe at a point within the Well, and maintaining an air cap below said seal between it and said body of liquid, compressing gas in said pipe above said Seal to a pressure of at least 1,000 lbs. per square inch while maintaining the pressure of said air cap at not more than about 1/10 of said pressure above said seal and suddenly releasing said pressure through said seal.

6. A process according to claim 5 in which said gas compressed in said pipe is air.

References Cited by the Examiner UNITED STATES PATENTS 2,560,901 7/51 Smith 166-155 3,033,286 5/62 May 166--42 X 3,066,734 12/62 Meiklejohn l66-42.1 3,101,117 8/63 Scott et al. 166 42,1 X

CHARLES E. OCONNELL, Primary Examiner.

NORMAN YUDKOFF, Examiner. 

1. A PROCESSS FOR FRACTRUING WELLS WHICH COMPRISES RUNNING A HIGH-PRESSURE PIPE INTO THE WALL AND PROVIDING A SEAL BETWEEN THE HIGH PRESSURE PIPE AND THE WELL WALL ABOVE THE STRATA TO BE FRACTURED, MAINTAINING BODY OF LIQUID IN THE WALL AT THE LEVEL OF THE STRATA TO BE FRACTURED SEALING THE BORE OF SAID PIPE AT A POINT WITHIN THE WELL AND MAINTAINING A GAS CAP BELOW SAID SEAL BETWEEN IT AND SAID BODY OF LIQUID, COMPRESSING GAS IN SAID PIPE ABOVE AID SEAL TO A PRESSURE OF AT LEAST 1,000 LBS. PER SQ. INCH WHILE MAINTAINING THE PRESSURE OF SAID GAS CAP AT NOT MORE THAN ABOUT 1/10 OF SAID PRESSURE ABOVE SAOD SEAL AND SUDDENLY RELEASING SAID PRESSURE THROUGH SAID SEAL. 